1. Field of the Invention
The present invention relates to multiple panel liquid crystal display (LCD) devices with a plurality of LCD panels bonded and united into a single integral large size display.
2. Discussion of the Background
Conventionally, cathode-ray tube (CRT) units, LCDs and plasma display devices have been widely used as output units for visual representation of images in audiovisual (AV) equipment and office automation (OA) equipment. The trend of these display devices is for less weight, less thickness, higher precision, and larger screen size.
When a large screen display device using a single piece of LCD panel is manufactured, the uniformity of the resultant display screen may decrease. To avoid this difficulty, a large screen display device is typically a multiple panel type which includes a plurality of display panel modules organized into a two-dimensional (2D) matrix form.
One typical prior known large screen LCD device is shown in FIG. 19a, which depicts in a cross-sectional view the edge section of one of multiple LCD panels used therein. A plan view of the part is shown in FIG. 19b.
As shown in FIG. 19a, two dielectric substrates 180, 181 are laminated above each other and bonded together by a chosen sealing material 182 at the edges thereof. However, as shown in FIG. 19b, when seen from a planar viewpoint, the sealing material 182 remains irregular in expansion along the surface. Thus, the width of a bonding section is required to be carefully designed in view of such expansion irregularity of the sealing material 182.
In the case a plurality of panels are bonded together on the same plane, the width of a black matrix is typically determined so that this width covers a corresponding bonded section rendering it invisible. More specifically, as shown in FIG. 19c, which illustrates a top plan view and side view of multiple panels bonded together, a certain part D including a substrate junction width DB and liquid crystal seal widths DS1, DS2 (D=DB+DS1+DS2) is defined as the junction region. This junction width D is the width of such black matrix in the junction region.
FIGS. 20a-20c are a side view of a substrate before cutting, a side view during cutting of the substrate and a top plan view of the substrate, respectively, illustrating an irregularity of the expansion of the sealing material at a cut edge of the substrate processed using a prior art cutter machine. Also, as shown in FIG. 20, using cutting machines, such as a dicer 192, can result in a discontinuous fracture or fault 193 (referred to as "burr" hereinafter) on the substrate edge surface. This is another factor that determines the junction width D. In such region with the burr 193 created, it is difficult to fabricate pixel electrodes so that this region is left as a non-displayable region in most cases.
In this way, the black-matrix width is determinable by either one of the irregular sealing material expansion region and the burr region which is wider than the other.
In such display devices with multiple LCD panels united by bonding, the junction regions D are uncontrollable for the transmissivity of light. This results in a region that is different in display image from those regions with liquid crystal, which in turn leads to a decrease in display characteristic such as contrast reduction. Thus, the need exists for forming a light shield film in junction regions on an array substrate that supports thereon an array of multiple LCD panels, or alternatively, on opposed substrates opposing the array substrate.
In addition, it is also necessary even for a part other than the junction regions to selectively provide a similar light shield film overlying a pattern of electrical interconnection leads in order to eliminate leakage of light rays from nearby lead portions. Unfortunately, this does not come without an accompanying penalty: when the light shield film is varied in pattern width and period between junction regions and the remaining regions, the light shield film pattern becomes observable lower in the quality and precision of images displayed.
To avoid this problem, one approach is to fabricate a specifically designed light shield pattern that is kept identical in width between junction regions and the remaining, non-junction regions, i.e., displayable regions. Even in this case, however, the junction region width D is approximately 0.3 millimeters (mm); accordingly, use of such "wide" light shield pattern on the entire surface of a multipanel display device reduces the total aperture ratio of displayable regions. The less the aperture ratio, the less the resultant brightness. Thus, a light source behind the panels, i.e., backlight, must be enhanced in intensity of output light. Obviously, this results in an increase in power dissipation.